Massage & Bodywork

May/June 2011

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functional anatomy BY CHRISTY CAEL TIBIALIS ANTERIOR The tibialis anterior is a large, superfi cial muscle on the front of the leg. The muscle belly begins near the lateral tibial condyle, following the lateral edge of the tibial shaft prior to inserting on the foot. The peroneus longus, a lateral leg muscle, inserts on the bottom of the foot at the same location as the tibialis anterior. Together, these two muscles form the anatomical stirrup, which loops around the midfoot and helps control its movements. The function of the tibialis anterior varies according to foot position. If it is free (not planted), the muscle insertion moves toward the origin, raising the foot up (dorsifl exion). This prevents the toes from catching on the ground during the swing phase of gait. Maintaining a dorsifl exed foot also situates the heel to strike the ground fi rst and positions the foot optimally for transition from heel strike to stance phase. When the foot is fi xed or planted, the TIBIALIS ANTERIOR Actions • Dorsifl exes the ankle • Inverts the foot Attachments • Origin: Lateral condyle and proximal half of tibia and interosseous membrane • Insertion: Plantar surface of medial cuneiform and base of fi rst metatarsal origin of the tibialis anterior moves toward the insertion, pulling the leg over the foot (also called dorsifl exion). This occurs as weight is accepted during the stance phase of gait. Once heel strike occurs, the tibialis anterior continues to contract, pulling the proximal tibia and center of gravity over the foot. The body is then positioned so the strong posterior leg muscles can begin the push-off phase of gait (plantarfl exion). Innervation • Deep peroneal nerve • L4–L5 earn CE hours at your convenience: abmp's online education center, www.abmp.com 91

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